The pouring of a molten material such as metal, for example, into a casting mold is a significant process variable that influences the internal soundness, surface conditions, and mechanical properties, such as tensile strength, porosity, percent elongation, and hardness, of a cast object. Many different designs for dipping/pouring ladles exist and are used in the foundry industry. Foundries typically use either a high pressure die casting (HPDC) process or a gravity pour casting method. Ladles are typically used in foundries for transporting pre-measured quantities of molten metal from a holding furnace to a casting machine. Molten metal is then poured from the ladle into a receptacle of the casting machine, for example into a shot sleeve in an HPDC process or a pouring basin in a gravity pour casting process. For large scale production casting processes, the ladle is normally mounted on a mechanical or robotic handling device, which is programmed to dip the ladle into the holding furnace to obtain a desired amount of molten metal. The robotic handling device then transports the metal to the casting machine and causes a pouring of the metal from the ladle into the casting machine.
Using conventional casting methods, casting ladles, and robotic handling devices, a great deal of turbulence can be generated while dipping the ladle into the holding furnace. For aluminum alloys, this turbulence can cause the formation of oxides, commonly referred to as dross, or other impurities that may adversely affect the quality of the casting. Electromagnetic pumps have been increasingly used in transferring molten metal to a casting mold. Since the electromagnetic pump is immersed in the molten metal, surface turbulence and the generation of oxides associated with a traditional ladle are minimized. However, electromagnetic pumps may be expensive and difficult to maintain and repair. Furthermore, the electromagnetic pump needs to be energized at all times to generate a bias voltage to minimize oxide formation in the electromagnetic pump and launder system. Also, cooling air required by electromagnetic pumps may create a variation in the temperature of the molten metal from an initial melt temperature.
Additives may be introduced to the molten metal to modify microstructure and to add strength to a casting formed from the molten metal. Additives include those such as titanium carbon aluminum, titanium aluminum, aluminum strontium, and titanium boron. The additives act as nucleating agents within the molten metal to control crystal formation during solidification of the molten metal. Additives such as titanium boron tend to evaporate quickly when added to a heated ladle. Therefore, the additives must be strategically added to the molten metal to ensure that the additive does not evaporate prior to mixing with the molten metal, and the additive must be adequately and uniformly mixed with the molten metal. Without proper mixing of the additive(s) with the molten metal, an undesirable casting may be produced.
It would be desirable to provide an improved pour ladle that addresses the disadvantages of conventional pour ladle and electromagnetic pumps while ensuring a desired introduction and mixing of an additive into a molten metal. Thus, it would be desirable to provide an apparatus and method for quiescently filling a ladle with molten metal and an additive, and for transferring the molten metal from the ladle to a casting mold to minimize turbulence in the molten metal to minimize defects in the desired cast object formed by a tilt pour molding process.